The invention concerns high-voltage and very high-voltage transformers, notably, those used to supply voltage to X-ray tubes and, in particular, a winding for such a high-voltage and very high-voltage transformer.
An X-ray tube comprises, in a vacuum chamber, a cathode that emits a beam of electrons to an anode (or target) comprising a rotating disk coated with a material such as manganese. An electric field is created between the cathode and the anode by applying between those two elements a voltage on the order of one hundred kilovolts or more in order to accelerate the electrons emitted by the cathode. The point of impact of the accelerated beam of electrons on the rotating disk causes the anode to emit X-rays.
In order to obtain the high and very high voltages of one hundred kilovolts or more from an input voltage, it is desirable to have rectifier circuits connected to transformer windings. The transformer windings are subject to very high voltages, so that it is desirable to insulate winding turns from one another with a sufficient thickness of material which should be a good electric insulator in order to prevent electric failure, while having good thermal conductivity to carry off or dissipate heat. For that purpose, one ordinarily uses paper placed between the layers of turns and dielectric oil that fills the whole chamber in which the transformer is immersed. However, this technique does not make it possible to effectively carry off or dissipate the heat due to heating of the windings, that may be caused by an electric current. Furthermore, in some applications it is required that radiological examination be made, notably, in the case of scanners, more and more rapidly, for example, four times faster then previously, in order to reduce operating cost, which results in dissipating more heat per unit time.
In the present state of the art, one solution to that problem is to increase the volume and weight of the transformer.